In the field of indoor positioning, efforts to improve precision by processing various signals including infrared rays, ultrasonic waves, magnetic fields, Wi-Fi, vision, and the like, have been continued. As smart phones in which Wi-Fi modules are embedded are widely used, the easiest approach for indoor positioning is a method using fingerprints of Wi-Fi Access Points (APs).
The fingerprinting method generates an indoor magnetic field map in advance and estimates a location by comparing a value measured by the geomagnetic sensor of a smart phone with the information in the map. According to Bell Laboratories in the U.S., such a fingerprinting method based on Wi-Fi has high precision, with a position error of only 1 to 2 m. However, maintenance is expensive, and localization is slow because the size of the map to be generated is very large.
Most conventional indoor positioning techniques require the construction of infrastructures in advance. In other words, the locations of Wi-Fi APs in a building must be known, and without such information, neither the localization of a user in the building nor recommendations based on the location of the user is possible. Also, APs are installed in places where the interference of APs from components of the building is minimized, APs may be easily connected, and the aesthetic appearance of the interior is not spoiled by the installation of APs, rather than being installed at regular distances. Furthermore, the locations of APs may often change due to the failure and replacement thereof. Therefore, even if the locations of APs in a building are detected in advance, additional effort to maintain the information is required.
The present invention detects the probabilistic locations of APs based on information collected from multiple user terminals even if there is no information about the locations of APs in a building, and proposes an indoor localization technique based on the information about the APs. Also, based on this indoor localization technique, the present invention intends to disclose a technique for recommending locations according to user preference and the current location of a user when the user enters a certain level of a building that has multiple levels.
As a related art of the present invention, there is Korean Patent Application Publication No. 10-2011-0133337, disclosed at Dec. 12, 2011 and titled “method and apparatus for providing advertisement based on position information of subscriber”.